Wiring 24v NPN Proximity Switch to 5v BOB - Why does'nt it work

[m_c]

I hope you mean +ve and not -ve.
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Best to go back to basics, wire up just the power and gnd to the sensor, and use a multimeter to check that the output is switching. Provided that works, connect it to the BOB.

[MikeyC38]

These proximity switches come in so many flavours. The switch the OP is using switches to ground and an internal resistor makes no sense; the switch in the previous post switches to the supply rail and maybe an internal resistor is more useful.

If you use the NC version of the OP's switches, wired as suggested in series with the BOB input, you can connect a number of them to a single input. I have tested four in series, using 24V and a CSMIO, and that seems to work fine. Using the OP's NO switches, you would have to wire them in parallel but you lose the "fail safe" feature of NC switches.

Hi Neale - I gave up on this for a while but now my machine is working nicely I really do need to get my "fish brain" around this and get the homing set up with these proximity switches so that I can do auto tool setting height etc. So if I understand your post correctly I need to do this as shown in the attached picture



Choosing the appropriate value of R drops the voltage down enough for the input and away we go (hopefully!) .

I really appreciate all the posts from you guys on this.

Kind Regards
Mike

[m_c]

Without re-reading the entire thread, NPN means it's switches the signal wire to ground.

So connect the sensor +VE to 24V, then the Gnd/0V to both the 24V supply GND/0V, and the BOB GND/0V (best to join both power supply GNDs at a common point).
Then connect the sensor signal wire to the Gnd/0V/- side of the opto input, and 5V to the 5V/+ side of the opto input.